A common roller blind is generally classified as a manual one and an electric one. The roller blind shown in FIG. 1 is a manual roller blind. The upper end of a common curtain 4 is fixed to a first circular tube 1 through an adhesive tape and the lower end of the common curtain 4 is fixed to a bottom bar 5. A user can pull a chain to rotate a driver which subsequently rotates the first circular tube 1 to roll up the common curtain onto the first circular tube 1 or to unfold the common curtain 4 away from the first circular tube 1. In this way, the user can choose to roll up or show the common curtain 4 with a size equivalent to that of the window.
FIG. 2 shows an electrical roller blind, which uses a tubular electrical motor to rotate the first circular tube 1. The user can choose to roll up or show one common curtain 4 with a size equivalent to that of the window.
Same or different curtain materials can be jointed together to form a common curtain 4 utilizing an adhesive or sewing or ultrasonic welding.
The present roller blind devices have their own drawbacks and problems, such as they can only roll up or show one common curtain 4 with a size equivalent to that of the window.